1. Technical Field
The present invention relates to a manufacturing method for a cooling unit, a cooling unit, an optical device, and a projector.
2. Related Art
As a cooling unit using a cooling fluid, there is one including a cooling plate in which a metal pipe serving as a cooling fluid channel is arranged between inner surfaces of a pair of metal plates combined to be opposed to each other. This cooling plate is manufactured by forming a pipe housing groove larger than the metal pipe at least in one of the pair of metal plates and integrally combining the metal pipe and the pair of metal plates. In a manufacturing process of the cooling plate, a pressurized fluid is supplied into the metal pipe after the combination and the metal pipe is expanded in diameter to cause the metal pipe to come into close contact with the pipe housing groove (see, for example, JP-A-2002-156195).
In the manufacturing method for a cooling unit, the pipe housing groove is formed in a reverse taper shape with respect to a mating surface of the metal plate and the metal plate and the metal pipe are combined by causing an edge portion (an undercut portion) of the groove to cut into the metal pipe at the time of the expansion of the diameter of the metal pipe.
However, in the manufacturing method, cutting needs to be performed using a special cutting tool for formation of the undercut portion. Thus, it is difficult to realize a reduction in cost.
In order to satisfactorily bring the metal pipe into close contact with the pipe housing groove, it is necessary to repeat the processing for expanding the diameter of the metal pipe plural times. This requires a great deal of time.
Moreover, when the metal pipe has a small diameter, it is difficult to expand the diameter of the metal pipe and an amount of deformation of the metal pipe tends to fluctuate. Thus, a gap is formed between the metal pipe and the pipe housing groove. As a result, deterioration in cooling performance of the cooling plate tends to be causes.